Anomalies in vortex states of cuprate superconductors

A maximum-entropy (ME) technique has been applied to transverse-field (TF) muon-spin relaxation (mu SR) data of several cuprate superconductors [1, 2]. For the RBa(2)Cu(3)O(7) (R1237) vortex states, we have seen low-field tails and cliffs in the ME field distribution estimates for TF mu SR data recorded near 5 K at 1 kOe. The sharp fall-off is only present when R is a magnetic ion (like Er or Gd), or occurs for Pr-doping in Y1237. The ME vortex field distributions of Bi2Sr2CaCu2Ox (Bi2212) and Tl2Ba2Ca2Cu3Ox (Tl2223) show no low field tails well below T-c, which is consistent with vortex pancake formation. ME transforms for Pb0.9In0.1 (a typical type-II superconductor) show the expected vortex field distributions. All the (magnetic) non-BCS like anomalies seen for the cuprate vortex states suggest that perhaps the cuprate superconductors are not (typical) type-II superconductors.